This relates to stereoscopic imaging systems and, more particularly, to stereoscopic imaging systems with convergence control for reducing conflicts between accommodation and convergence.
Modern electronic devices such as cellular telephones, cameras, and computers often use digital image sensors. Imagers (i.e., image sensors) may be formed from a two-dimensional array of image sensing pixels. Each pixel receives incident photons (light) and converts the photons into electrical signals. Image sensors are sometimes designed to provide images to electronic devices using a Joint Photographic Experts Group (JPEG) format.
Stereoscopic imaging (e.g., three-dimensional imaging) is becoming increasingly popular. In stereoscopic imaging, left and right images of a scene are captured from two difference perspectives. As a result, different depth planes in the scene are encoded in an image pair as differences in horizontal disparities. A converging depth plane has zero disparity (e.g., an object in the converging depth plane will have the same position in both the left and right images). Depths planes closer to an imager than the converging depth plane will be encoded as crossed disparities (e.g., disparities which induce the viewer's eyes to cross) and depth planes farther from the imager than the converging depth plane will be encoded as uncrossed disparities (e.g., disparities which induce the viewer's eyes to uncross). When stereoscopic images are displayed on a display, the encoded horizontal disparities (e.g., the differences between the left and right images of a scene) are perceived by viewers as different depth planes in front of and/or behind the display, resulting in the perception of a three-dimensional image.
Conventional stereoscopic camera systems include convergence control in which the location of the converging depth plane can be changed. In particular, some stereoscopic camera systems include manual controls that allow an operator to manually adjust the location of the converging depth plane (e.g., to adjust the distance from the stereoscopic camera at which objects in a scene will be in the converging depth plane and encoded with zero disparity). In other stereoscopic camera systems, the location of the converging depth plane is tied to a lens zoom setting (e.g., at a wide angle zoom, the converging depth plane is relatively close to the stereoscopic camera and, at a telephoto zoom, the converging depth plane is relatively distant from the stereoscopic camera).
One problem with viewing stereoscopic images and video is the conflict between accommodation stimuli and convergence stimuli. Accommodation is the change in focus of the lens of a user's eyes. Convergence is the movement (e.g., horizontal rotation) of the user's eyes to point to the same position in space. In the natural world, the cues for convergence and accommodation are consistent and the convergence and accommodation mechanisms are linked together. In stereoscopic imaging, however, convergence and accommodation stimuli are not linked, which can lead to conflicts and viewer discomfort.
When viewing a stereoscopic image on a display, a viewer's eyes focus on the display. If the viewer's eyes focus anywhere away from the display, the stereoscopic image would appear blurred. The display therefore serves as a cue for accommodation. In contrast, the horizontal disparities in the stereoscopic image (e.g., the differences between the left eye and right eye images) create convergence cues via the perception that the stereoscopic image extends in front of and behind the display, which guides the viewer's eyes away from the display. Once the viewer's eyes are guided away from the display (by convergence cues), the stereoscopic image will appear blurred and the accommodation cues will try to shift the viewer's focus back to the display. This conflict can make viewing stereoscopic images discomforting.
It would therefore be desirable to provide improved stereoscopic imaging systems with convergence control for reducing conflicts between accommodation and convergence.